Method for minimizing drill pipe failures



Feb. 14, 1961 A. P. HELDENBRAND 2,971,373

METHOD FOR MINIMIZING DRILL PIPE FAILURES Filed July 5, 1957 INVENTOR.A. I? HELDEN/SEA/VD ATTORNEY United States Patent METHOD non MINIMIZINGDRILL PIPE FAILURES Arthur P. Heldenhrand, SE. 35th, Oklahoma City,Okla.

Filed July 5, 1957, Ser. No. 670,069

5 Claims. (Cl. 73-99) This invention relates to an improved method andapparatus for minimizing failures of drill pipe of the type used inrotary drilling of oil and gas wells.

As it is well known in the oil and gas well drilling industry, drillpipe appearing to be in perfect condition often fails during a drillingoperation, resulting in an expensive and time consuming fishing job torecover the lost portion of the drill string. Many testing devices havebeen designed to test the pipe for hidden defects between drilling runswhile the pipe is on the surface of the ground. The majority of thesetesting devices rely upon the magnetic properties of the drill pipe andare effective only in locating severe pits or cracks in the drill pipe.Such testing devices do not indicate the presence of localized stressareas in the drill pipe, nor the minimum tension (either lengthwise orin torque) which the drill pipe will stand. Therefore, drill pipe whichhas been tested for cracks and corrosion will still frequently failduring a drilling operation.

It is a generally accepted theory that the joints in a drill stringwhich will withstand the least tension, in either a longitudinaldirection or in torque, will receive the major portion of the vibrationand twisting of the drill string and fail prior to failure of the otherjoints. Heretofore, however, this theory has not been fully used in thefield to anticipate drill pipe failures. It is known to place each jointof a drill string under longitudinal tension prior to running the pipein a well to determine whether the pipe meets the minimum tensionrequirements promulgated by API and the various drill pipemanufacturers. However, this method is ordinarily used only after thepipe has been run through at least one drilling operation, and themethod does not necessarily give an indication of the torque which thedrill pipe will withstand. When analyzed, it will be appreciated that ajoint of drill pipe permanently twisted, either intentionally or throughuse in a drilling operation, will have localized stress areas which arelikely to cause a failure of the pipe during a subsequent drillingoperation. It should also be noted that although the majority of drillpipe failures occur after the pipe has been in service for a period oftime, some failures occur during the first use of the drill pipe.Therefore, new drill pipe does not always meet the minimum tensionrequirements for the intended use, even though the walls of the drillpipe are not corroded or cracked in any manner.

The present invention contemplates a novel method of checking the drillpipe before and after it is run in a well to anticipate drill failures.In its broader aspects, this invention contemplates the determination ofthe amount of twist permanently induced in each joint of a string ofdrill pipe occurring through use of the pipe, whereby those jointshaving localized stress areas and which will be the most likely to failmay be discarded. I also contemplate tensile testing the drill pipeprior to running the drill pipe in a well to minimize failures of thedrill pipe during the initial use thereof. Further- "ice more, thisinvention contemplates novel apparatus for determining the permanenttwist of drill pipe.

An important object of this invention is to minimize drill pipe failuresand increase the economy of oil and gas well drilling operations.

Another object of this invention is to provide a novel method oflocating those joints in a drilling string which have localized stressareas and which will be the most likely to fail during a subsequentdrilling operation.

A further object of this invention is to determine the permanent twistinduced in drill pipe during use of the pipe in a drilling operation. Inconjunction with this objective, it is also an object of this inventionto determine those joints of drill pipe which do not meet the calculatedminimum tensile strength requirements for the pipe.

Another object of this invention is to provide simple and economicalapparatus for determining the permanent twist of a joint of drill pipe.

Other objects and advantages of the invention will be evident from thefollowing detailed description, when read in conjunction with theaccompanying drawings which illustrate my invention.

In the drawings:

Figure 1 is a longitudinal sectional view, partially in elevation, of apoint of drill pipe having a sighting device on one end thereof and atarget device on the opposite end thereof.

Figure 2 is an enlarged cross sectional view of the punching mechanismused for marking the ends of a joint of drill pipe.

Figure 3 is an enlarged plan view of a portion of the target device ofthis invention.

Referring to the drawings in detail, reference character 4 designates atypical joint of drill pipe having an internally threaded box 6 on oneend thereof and an externally threaded pin 8 on the opposite endthereof. It is to be understood that the specific design of the drillpipe 4 is immaterial, so far as the present invention is concerned. Asighting device, generally indicated at 10, is secured in the box 6 ofthe pipe 4; and a target device, generally indicated at 12, is securedon the pin 8 of the pipe. During testing of the pipe 4, the pipe will besupported in a substantially horizontal position by any suitablesupporting mechanism (not shown).

The sighting device 10 comprises an externally threaded tubular member14 of a size to be threaded into the box 6. A circumferential flange 16is formed on the outer end of the member 14 to abut the outer end of thebox 6 when the member 14 has been completely threaded into the box. Theouter end of the member 14 is suitably machined to provide acircumferential shoulder 18 which receives a complementary shoulder of atubular mandrel 20. It will be understood that the shoulder 18 alignsthe mandrel 20 with the member 14, whereby the longitudinal axis of themandrel 20 will be aligned with the longitudinal axis of the drill pipe4. Apertured plates 22 are secured in the inner end of the member 14 andthe outer end of the mandrel 20 to receive a suitable rod 24 and securethe mandrel 2t) rigidly on the shoulder 18 of the member 14.

The outer periphery of the mandrel 20 is machined smooth to slidinglyreceive a sleeve 26, with the sleeve 26 preferably being of a size toprovide a friction fit on the mandrel 20, whereby the sleeve 26 willtend to stay in any angular position on the mandrel 20 in which it isplaced. A suitable retaining ring 28 is threaded onto the outer end ofthe mandrel 20 to secure the sleeve 26 lengthwise on the mandrel againsta circumferential shoulder 30 at the inner end of the mandrel.

A tube or pipe 32 is secured on the outer periphery of the sleeve 26 bymeans of a suitable pad 34, with 3 the tube 32 extending radially fromthe sleeve 26. The pad 34 may be secured to the outer periphery of thesleeve 26 in any suitable manner, such as by bolts, and the tube 32 ispreferably welded to the pad 34. A tapered block 36 is secured in theinner end of the tube 32 to mate with the tapered inner end of atelescope support rod 38 which is telescoped into the outer end of thetube 32, whereby the support rod 38 is held in the tube 32 in a fixedangular position. A telescope 40 is supported by a bracket 42 on theouter end of the rod 38 in such a position that the telescope 40 extendsparallel with the longitudinal axis of the pipe 4. The bracket 42 may beof any desired construction to permit adjustment of the telescope 40,but preferably is constructed so that the telescope 40 can be secured ina fixed position on the rod 38, whereby the telescope will be trulyparallel with the longitudinal axis of the pipe 4. The rod 38 may beadditionally held in the tube 32 by means of a set screw 44 threadedthrough the wall of the tube 32, if desired.

Another tube or pipe 46 is secured to the tube 32 in such a manner as toextend substantially parallel with the telescope 40 and the longitudinalaxis of the pipe 4 and is utilized to receive a support arm 48 of apunch holding mechanism 50. The tube 46 may be welded to the tube 32 tomake a rigid connection, and the arm 48 may be secured in the tube 46 bya suitable set screw 52.

The punch holding mechanism 50 (see Fig. 2) comprises a hollow housing54 having a bottom wall 56 and open at its upper end. A bushing 58 isslidingly disposed in the housing 54 and issuitably bored to receive theupper enlarged portion of a center punch 60. The punch 60 extendsdownwardly from bushing 58 through an aperture 62 in the bottom wall 56of the housin 54. A button-like member 64 is threaded into the upper endof the bushing 58 to hold the center punch 60 in the desired position inthe bushing and to form a striking area for hand operation of the punch60, as will be more fully hereinafter set forth. The bushing 58 andpunch 60 are continually urged upwardly in the housing 54 by a suitablehelical compression spring 66 anchored between the bottom wall 56 andthe lower end of the bushing 58. A handle 68 extends transversely outfrom the bushing 58 through a C-shaped slot 70 in one side of thehousing 54. It will be apparent (see also Fig. 1) that when the handle68 is in the lower horizontal leg of the slot 70, the center punch 60will protrude below the bottom wall 56 of the housing 54; whereas whenthe handle 68 is in the upper horizontal leg of the slot 70, the centerpunch 60 will be contained wholly within the housing 54. When the handle68 is in the vertical leg of the slot 78, the bushing 58 and centerpunch 60 may be moved up and down to alternately extend and retract thecenter punch 60.

From the foregoing it will be apparent that the sighting device it) ismounted in the box 6 of the pipe 4 and is constructed in such a mannerthat the telescope 40 extends parallel with the longitudinal axis of thepipe 4. The supporting sleeve 26 may be turned on the mandrel 20 to movethe telescope 40 around the axis of the pipe 4 for positioning thetelescope 40 in the desired angular position. The punch holdingmechanism 58 is supported on the instrument supporting sleeve 26 insucha position that the center punch 60 is preferably in line with thetelescope 40 and the longitudinal axis of the pipe 4.

The target device 12 comprises an internally threaded member 74 of asize to be threaded onto the pin end 8 of the pipe 4. An outwardlyfacing circumferential shoulder '76 is machined on the outer end of themember 74 to receive the inner end of a tubular mandrel 78. The innerdiameter of the mandrel 78 is such to provide a snug fit of the mandrelon the shoulder 76, whereby the mandrel 78 will be aligned with thelongitudinal axis of the pipe 4. Apertured plates 80 are secured in theouter end of the member 74 and the outer end of the mandrel 78 toreceive a suitable bolt 82, whereby the mandrel 78 will be rigidlysecured on the member 74.

The outer periphery of the mandrel 78 is machined smooth to receive aninner support sleeve 84. Another support sleeve 86 is telescoped overthe inner sleeve '84, with the fit of the sleeve 84 on the mandrel 78and the fit of the sleeve 86 on the sleeve 84 being such that thesleeves 84 and 86 will be retained in their relative angular positionsby friction, yet the sleeves 84 and 86 may be turned by hand. The innerend of the sleeve 84 has a outwardly extending flange 88 thereon whichabuts an outwardly extending flange 90 formed on the inner end of themandrel 78. A suitable retaining ring 92 is threaded onto the outer endof the mandrel 78 to retain the sleeves 84 and 86 in the desiredlongitudinal positions on the mandrel.

A tube 94 is secured on the flange 88 of the inner support sleeve 84 bymeans of a suitable bolt 96. The bolt 96 is threaded into the flange 88to retain the tube 94 in a radial position with respect to the sleeve84, and, of course, the tube 94 will be turned about the axis of thepipe 4 upon rotation of the sleeve 84. Another tube 98 is secured in ahorizontal position on the tube 94 to receive and support another punchholding mechanism 50 of the type previously described. The enter punch60 of the respective punch holding mechanism 50 will be retained in linewith the tube 94 and the longi tudinal axis of the drill pipe 4. a

A target supporting tube 100 is secured in a radial direction on theouter periphery of the outer support sleeve 86 by means of a suitablepad 102. The base portion 104 of a target 106 is telescoped into thetube 100 to support the target radially with respect to the sleeve 86and the pipe 4. It will 'be understood that the target 186 will berotated about the axis of the pipe 4 upon turning of the sleeve 86 onthe inner sleeve 84, or upon turning of both sleeves 84 and 86. Supportrod 104 may be secured in the tube 100 by a suitable set screw 108 toprevent the target 106 from falling out of the tube 100.

As shown most clearly in Fig. 3, a latch 110 is pivotally secured bybrackets 112 on the target supporting tube 100, whereby the latch 110will pivot radially with respect to the sleeves 84 and 86 and extendtoward the tube 94 mounted on the inner sleeve 84. The outer end 114 ofthe latch 110 is suitably designed, such as being bifurcated, to extendaround the tube 94 when the latch is in a horizontal position, wherebythe sleeves 86 and 84 will be locked together for simultaneous movementon the mandrel 78. A suitable stop (not shown) will be provided on thetube 94 or in the bracket 112 to limit the downward movement of thelatch 110 and retain the latch in a horizontal position as shown inFig. 1. However, the latch 110 may be swung upwardly, or outwardly, oifof the tube 94 to unlock the sleeves 84 and 86 for separate movementthereof.

As also shown in Fig. 3, degree markings 116 are provided on the innerend of the outer supporting sleeve 86, and a suitable zero marking (notshown) is provided 1 on the flange 88 of the inner sleeve 84, wherebythe relative positions of the sleeves 84 and 86 may be determined. Themarkings 116 are arranged in such a manner that the zero degree mark onthe sleeve 86 will be aligned with the zero marking on the flange 88 ofthe inner sleeve 84 when the latch 100 is connected with the tube 94. Inthis position of the target device, the respective punch 60 will be inline with the axis of the pipe 4 and a suitable vertical line (notshown) provided in the center of the target 106.

In practicing the method of this invention, I prefer to place each jointof a string of new drill pipe under tension along its longitudinal axis.Such a tensioning operation maybe performed by use of a tension machineas disclosed in my United States Patent No. 2,757,536. Basically, eachjoint is placed under tension by threading pulling members on theopposite ends of the joint and then forcing the pulling members apart.According to the method of the present invention, each joint of a stringof drill pipe is placed under tension to its actual minimum yield point,and such information is suitably recorded. Each joint will, of course,be marked with a suitable identifying number or symbol so that eachjoint can be later identified with its original tensile strength. Thosejoints which begin to yield before the force exerted equals the minimumyield strength specified by API (that is, those joints not meeting APItensile strength requirements) should be eliminated and not used in thedrill string. Those joints meeting or exceeding API specifications areused in the drill string. The fact that some joints exceed APIspecifications merely indicates that they are made out of better steel.In each instance, the actual tensile strength of each joint is recorded,as indicated above.

Following the tensioning of the drill pipe, the sighting device and thetarget device 12 are secured on the opposite ends of one of the jointsof drill pipe, in the manner illustrated in Fig. l. The latch 110 of thetarget device 12 is secured on the supporting tube 94 of the respectivepunch holding mechanism 50 to align the target 106 with the respectivepunch 60. Also, the handle 68 of each punch holding mechanism 50 ismoved into the upper horizontal leg of the respective slot 70 to retainthe punches 60 in the housings 54 out of contact with the pipe 4. Thesupport sleeves 84 and 86 are then moved on the mandrel 78 until thetarget 106 is aligned with the telescope 40. It will be understood thatone operator watches through the telescope 40 while another operatorturns the sleeves 84 and 86. When the target and telescope are aligned,the handle 68 of each punch holding mechanism 50 is turned into thevertical portion of the respective slot 70; whereupon an operatorstrikes the button 64 of each punch mechanism to drive the inner ends ofthe punches 60 into the outer periphery of the pipe 4 and provide anindentation in each end portion of the pipe. Since the punches 60 arealigned with the telescope 40 and the target 106, the indentations madeby the punches will be aligned with the axis of the pipe 4. The handle68 of each punch mechanism is then again moved back into the upperhorizontal leg of the respective slot 70, and the sighting device 10 andtarget de vice 12 are detached from the joint 4. This operation isrepeated for each joint of the drill pipe to be run into a well througha drilling operation. If desired, a circular indentation (not shown) maybe punched into the pipe 4 around each of the indentations made by thepunches 60 to facilitate subsequent location of the markings.

In addition to tensioning and placing aligned marks on each joint of thedrill pipe, I also prefer that the length of each joint of the drillpipe be measured, and such information suitably recorded along with theactual tensile strength of each joint. The joints of drill pipe are thenrun in a well in tandem relation in the usual manner through a drillingoperation.

Upon removal of the drill pipe from the well, each joint is disconnectedfrom the drill string, and the sighting device 10 and target device 12are again attached to a joint in the manner shown in Fig. 1. Uponassembly of the sighting device 10 in the box 6 of the joint 4, thesupport sleeve 26 is turned on the mandrel 20 until the respective punch60 is directly opposite the indentation previously made in the pipe 4.When locating the indentation, the respective handle 68 is turned intothe vertical portion of the respective slot 70 and the center punch 60held into contact with the outer periphery of the pipe. When the centerpunch is seated in the indentation, the respective handle 68 is movedinto the lower horizontal leg of the respective slot 70 to hold thecenter punch in the indentation and align the telescope 40 in the sameposition it was when the indentation was made.

Upon assembly of the target device 12 on the pin 8 of the joint 4, theinner sleeve 84 is turned on the mandrel 78 until the respective punch60 is aligned with the respective indentation in the pipe. The handle 68is then moved into the lower horizontal leg portion of the slot 70 tohold the center punch 6t) in the indentation. The latch is thendisengaged from the tube 94 and the sleeve 86 is turned on the sleeve 84until the target 106 is aligned with the telescope 4-0. Whereupon, therelation of the markings 116 on the sleeve 86 with respect to the zeromarking on the inner sleeve 84 Will indicate the amount of permanenttwist induced in the pipe 4 by the drilling operation.

When such measurement is completed, the punches 60 are retracted intohousings 54 and locked into position by the handles 68, and the sleeves84 and 86 are aligned, with the latch 110 again engaged with the tube94. These operations are repeated on each joint of the drill piperemoved from the well, whereby the permanent twist of each joint ofdrill pipe will be determined. Those joints having been twisted asubstantial degree will have localized stress areas which make thejoints likely to fail in a subsequent drilling operation; whereas thosejoints having negligible twist will be in substantially the samecondition as prior to the first drilling operation and will be suitablefor subsequent use. It will be understood that the permissible twistwhich may be induced in a joint of drill pipe will be dependent on thematerials of construction, size of the pipe and many other factors.Therefore, at this state of the art, no maximum tolerable permanenttwist can be specified for all drill pipe used. As a practical matter,those joints of drill pipe permanently twisted a substantially greateramount than the other joints of a drill string should be discarded andnot reused in a drilling operation. Generally speaking, the ten percentof the joints having the highest permanent twist will be the most likelyto fail and should be discarded prior to further drilling.

When the drill pipe is removed from a well, the length of each jointshould also be measured and compared with the length of the joint priorto the drilling operation. Those joints which have been stretchedthrough use in the well will undoubtedly take the major portion of thestretch of the drill string during a subsequent drilling operation.Therefore, those joints which were permanently stretched by the firstdrilling operation would be likely to fail during a subsequent operationand should be discarded.

As further assurance that the drill pipe will not fail in a subsequentdrilling operation, each joint is preferably again placed underlongitudinal tension in the manner previously described. Each joint isplaced under tension to its actual minimum yield point, and the resultobtained is compared with the original tensile strength of the joint.Those joints which do not meet the minimum API tension specificationsare discarded as before, since such joints would take the majority ofthe vibration and tension of the drill string and be the most likely tofail. When a used joint of drill pipe does not meet the minimumlongitudinal tension requirements, it usually indicates that the jointis worn on its outer surface or corroded through use.

The changes in tensile strength of drill pipe will vary with drillingconditions, but I have found that the variations usually follow apattern, with the normal variations in a localized area being fairlyuniform. In some areas, such as West Texas, when wear or corrosion doesnot take place, drill pipe is work-hardened through use, and the tensilestrength of each joint measurably increases through use. However, whenexcessive workhardening occurs, the drill pipe becomes brittle and islikely to fail, particularly if subjected to rather sudden blows orshocks. Therefore, I prefer to discard those joints wherein the tensilestrength has been raised more than twenty percent through use. Thosejoints having substantially the same, or an increase of twenty percentor less in tensile strength, may be re-used in a drilling operation witha minimum risk of failure.

In other areas, such as in Kansas, the tensile strength of drill pipewill decrease slightly, even though the pipe is not worn or corroded. Inthese areas, the drill pipe should be removed from the drill string whenits actual minimum tensile strength decreases more than five percentfrom the original tensile strength. Thus, in any area, the drill pipeshould be removed from the drill string when its minimum tensilestrength increases more than twenty percent or decreases more than fivepercent from its original tensile strength. It is to be understood thatthe time the pipe has been in service and the amount of footage the pipehas drilled are of no consequence in determining the suitability of thepipe. If the pipe is placed in use and the tensile strength changes morethan specified above, it should be removed from the drill string.

From the foregoing it will be apparent that the present inventionprovides a novel method and apparatus for minimizing drill pipefailures. The method may be practiced on drill pipe at any stage of awell drilling operation. The method gives evidence of localized stressareas in drill pipe induced through use of the drill pipe, whereby thosejoints most likely to fail during a subsequent drilling operation may beidentified and discarded or removed from the drill string. Also,experience has shown that new drill pipe having the prescribedlongitudinal tension, as described above, will ordinarily be suitablefor use in at least one drilling operation, with a minimum likelihood offailure of the pipe. It will further be apparent that the presentinvention provides a novel apparatus for placing aligned marks on theopposite end portions of joints of pipe and for determining the amountof permanent twist induced in a joint of drill pipe.

Changes may be made in the combination and arrangement of parts orelements and steps or procedures heretofore set forth in thespecification and shown in the drawings without departing from thespirit and scope of the invention as defined in the following claims.

I claim:

1. A method of minimizing failures of drill pipe, comprising the stepsof:

(a) placing aligned marks on the opposite ends of each joint of thedrill pipe,

(12) running the drill pipe in a well through a drilling operation,

removing the drill pipe from the well and disconnecting each joint,

(d) measuring the angular displacement of said marks to determine theamount of permanent twist in eachjoint resulting from the drillingoperation, and

(e) discarding those joints having the largest permanent twist.

2. A method of minimizing failures of drill pipe, comprising the stepsof:

(a) tensioning each joint of the drill pipe to its actual minimum yieldpoint,

(b) discarding those joints not meeting minimum yield strengthrequirements,

(0) measuring the length of each joint,

(d) placing aligned marks on the opposite ends of each joint,

(e) running the marked joints in a well drilling op eration,

(f) removing the drill pipe from the well,

(g) measuring the length of each joint removed and the angulardisplacement between said marks, and

(h) discarding those joints either permanently stretched or twisted.

3. A method as defined in claim 2 characterized further in that eachjoint removed from the well is again tensioned to its actual minimumyield point, discarding those joints not meeting minimum yield strengthrequirements by said second tensioning, and discarding those jointswherein the minimum yield strength has increased more than twentypercent or decreased more than five percent from the strength thereofdetermined by the firstmentioned tensioning.

4. A method as defined in claim 1 characterized further in that saidmarks are placed on each joint by mounting a sighting device on one endof the joint and a target device on the opposite end of the joint,aligning the sighting and target devices, and punching an indentation inthe outer periphery of the joint adjacent each end of the joint on theline of the sighting and target devices.

5. A method as defined in claim 4 characterized further in that theangular displacement of said indentations is measured by mounting thesighting and target devices on the opposite ends of the joint, with eachdevice aligned with the indentation adjacent thereto, then turning thetarget device until the devices are aligned, and measuring the degreesthe target device was turned.

References Cited in the file of this patent UNITED STATES PATENTS958,736 Ferris May 24, 1910 11,667,995 Steinle May '1, 1928 2,673,613Irwin Mar. 30, 1954 2,712,756 Greer et al. July 12, 1955

